Microvascular Free Tissue Transfer / orthodontic courses by Indian dental academy

Microvascular Free Tissue Transfer

INDIAN DENTAL ACADEMY

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History

Early 1900’s Alexis Carrel1950’s Jacobsen and Suarez—anastomoses in animals1959 Seidenberg– free jejunum segments to repair pharyngoesophageal defects (human)1972 McLean and Buncke – omental flap to cover a cranial defect (first “microvascular” flap)1973 Daniels and Taylor– “free flap”

First free cutaneous flap1976 Baker and Panje– first free flap in head and neck cancer reconstruction

Groin flap pedicled on the circumflex iliac artery


Advantages of free tissue transfer

Two team approachImproved vascularity and wound healingLow rate of resorptionDefect size of little consequencePotential for sensory and motor innervationPermits use of osseointegrated implants


Advantages of free tissue transfer

Wide variety of available tissue typesLarge amount of composite tissue Tailored to match defectWide range of skin characteristicsMore efficient use of harvested tissueImmediate reconstruction


Recipient vessels

ArteriesSuperficial temporal system –scalp and upper faceFacial artery—midface and cervical region (atherosclerosis common)Superior thyroid or lingual artery—lower cervical regionOther: thyrocervical trunk, external carotid, common carotid


Recipient vessels

VeinsExternal jugularBranches of internal jugular (common facial)Internal jugularRetrograde (superficial temporal, thyroid)Transverse cervical, occipital (very small)


Recipient vessels after previous neck dissection

Gold standard: Angiogram (short-term injury to endothelium reported)Operative reportsLong-pedicled flapsThyrocervical trunk (transverse cervical), Occipital vessels, retrograde drainage (thyroid veins, superficial temporal), external carotid artery Contralateral vessels (recipient or graft)End-to-side anastomoses with large vessels Vein graftsArteriovenous loop (poorer results)


Vessel selection

Size Arterial vs.Venous

Atherosclerosis XRT-related changesVessel geometry (location and orientation)Vessel length


Vessel preparation

Arteries need to have strong pulsatile flow—cut until it flows. Cut back beyond branches or ligate them if sufficiently distant from the anastomosis site.AtherosclerosisIntimal inspectionDilationRemoving the adventitia


Irradiated vessels

Technically more difficult—effects appear specific to arteriesHigher incidence of atherosclerosisVessel wall fibrosis, increased wall thickness, more intimal dehiscenceNo reported difference in outcome of microvascular anastomoses (Nahabedian MY, et al., 2004, Kroll SS, et al 1998)Microvascular anastomoses tolerate XRT well long-term (Foote RL., et al., 1994)Require careful handling, cut off clot (teasing thrombi may denude vessel wall—”sticky” walls), smaller suture, needle introduced from lumen to outside wall (to pin intima to wall)


Prepare vesselsEvaluate vessel geometryTrim, irrigate, dilate

Partial flap insetting (bony cuts and plating done at donor bed, if necessary)Arterial vs. venous anastomosis first with early or delayed unclamping of first vessel showed no difference. (Braun, et al., 2003)

Anastomosis of remaining vesselComplete flap insetting

Microvascular Anastomosis


Microvascular surgical technique

Trim adventitia2-3mmGentle handling (no full-thickness)Trim free edge, if neededDissect vessels from surrounding tissues

Irrigate and dilateHeparinized salineMechanical dilation (1 ½ times normal –paralyses smooth muscle)Chemical dilation, if necessary

Suturing


Microvascular suture technique

3 guide sutures (120 degrees apart)Perpendicular piercingEntry point 2x thickness of vessel from cut endEqual bites on either sideMicroforceps in lumen vs. retracting adventitiaPull needle through in circular motionSurgeon’s knot with guide sutures, simple for othersAvoid backwalling—2 bites/irrigation


3 suture technique


Vessel size mismatch

Laminar flow vs. turbulent flow<2:1 – dilation, suture technique>2:1, <3:1 – beveling or spatulation (no more than 30 degrees to avoid turbulence)>3:1 – end-to-side


End-to-end vs. End-to-side

Recent reports indicate end-to-side without increase in flap loss or blood flow rate.End-to-side overcomes size discrepancy, avoids vessel retraction, and IJ may act as venous siphon.End-to-side felt best when angle is less than 60 degrees (minimize turbulence)Vessel incision should be elliptical, not slitCan use continuous suture technique


End-to-side Anastomosis


Continuous suture technique

May significantly narrow anastomosisMay be used on vessels >2.5 mmDecreases anastomosis time by up to 50%Decreases anastomosis leakageMost commonly used for end-to-side anastomoses with large vessels


Mechanical anastomosis

DevicesClipsCouplerLaser

ResultsIncreased efficiency and speed, use in difficult areasPatency rates at least equal to hand-sewn (Shindo, et al 1996, De Lorenzi, et al 2002)Can be used for end-to-end or end-to-side (DeLacure, et al 1999)Poorer outcome with arterial anastomosis—20-25% failure (Shindo, et al 1996, Ahn, et al 1994)


Vein grafts

Used in situation where pedicle is not long enough for tension-free anastomosisUsually harvested from lower extremity (saphenous system)Valve orientation is necessaryAvoid anastomosis at level of vein valveKeep clamps in place until both anastomoses sewnPrognosis for success controversial (Jones NF, et al., 1996, German, et al. 1996)

Recent literature


Microvascular Hints & Helps

Use background to help visualize sutureDemagnetize instruments, if neededMay reclamp vessels for repair after 15 minutes of flowReclamp both arterial and venous vessels when revising venous anastomosisSupport your hands and hold instruments like a pencil


Ischemia

Primary and secondaryPrimary: 2.25-6 hoursSecondary: 1-12 hours Interrelation No flow phenomenon

Cold vs. normothermic In vitro studies show benefit to cooling of flapsIn vivo studies show surface cooling (<4hr ischemia time) does not adversely effect flap success (Shaw W. et al 1996)

Tissue specific critical ischemia timesMetobolic rate dependent

Perfusates (UW, tissusol, Viaspan, Heparin)Literature unclear


Anastomotic failure

• 93-95% success rate expected• Venous thrombosis:Arterial thrombosis 4:1,

ateriovenous loop, tobacco use significant factors (Nahabedian M., et al, 2004) Other literature indicates 9/10 thromboses secondary to venous thrombus

• Tobacco use as contribution controversial (4/5 failures in Nahabedian study - venous thrombosis)

• Venous occlusion, Delayed reconstruction, Hematoma significant factors in breast free tissue recon. (Nahabedian M., et al, 2004)

• Salvage 50% in breast reconstruction• Age, prior irradiation, DM (well-controlled), method

of anastomosis, timing, vein graft, and specific arteries/veins not felt to contribute to failure rate


Anastomotic Failure--timeline

15-20 minutes<72 hours5-7 days>8 days

Thin vs. thick flaps


Thrombus formation

Injury to endothelium and media of vesselMechanical vs. thermal

Error in suture placementBackwall or loose suturesEdges not well-aligned (most common in veins—most common site of thrombus)Intimal discontinuity with exposure of media

Oblique sutures, large needles, tight knotsInfectionHypovolemia and low flow states

Nitroprusside at dose to decrease arterial pressure by 30% causes severe reduction in flap blood flow (40%) (Banic, et al. 2003)Vessel geometry (kinking, tension)


Vessel spasmCauses

TraumaContact with bloodVasoconstrictive drugs

Phenylephrine--dose causing 30% increase in arterial pressure shows no effect on flap circulation (Banic A, et al., 1999) Nicotine

Temperature, dryingTreatment

WarmthXylocainePapavarine, thorazineVolume repletion


Treatement for anastomotic failure

Revision of anastomosesExploration of woundStreptokinase, urokinase, rt-PA (Atiyeh BS, et al 1999)Leech therapyWound careStatistics

Revisions successful in 50%Revisions less successful after first 24-48hr>6 hrs of ischemia leads to poor survival12 hrs of ischemia leads to “no-flow” phenomenonAfter 5 days almost all flaps in rabbit model survived with loss of artery or vein (but not both)—this is rational for other modalities after 48 hours


Post-operative care

AnticoagulationAttention to wound careFlap monitoring Nothing around neck that might compress pedicleAntibiotics Hemoglobin/intravascular volume—literature unclear (Velanovich V., et al 1988, Quinlan 2003)

No pressors/nicotine/cooling of flap (literature unclear)


Anticoagulation

RheologyRBC concentrationPlasma viscosityRBC aggregationRBC deformability Other (platelets, thrombogenic mediators)

AgentsAspirinHeparinDextranOther

IndicationsHypercoagulable state (Friedman G, et al, 2001)Excessive vessel trauma

Complications


DextranMacromolecule which is a compound of glucose subunitThought to improve RBC flexibility, increase electronegativity of vessel wall (which decreases platelet adhesion), act as intravascular volume expander, decrease RBC aggregationShown to decrease clotting secondary to exposed collagen in rabbit arteries. Little effect on platelet, rather inhibits fibrin stabilization of thrombi (Weislander, JB, et al., 1986)No effect on overall flap survival when compared with aspirin. Systemic complications 3.9-7.2 times more common with dextran infusion (Disa J., et al, 2001)Complications can include renal damage, anaphylactic shock, congestive heart failure, MI, pulmonary edema, pleural effusion, pneumonia


Aspirin

Prevent platelet thrombosisInhibits arachidonic acid to prostaglandin synthesis on the platelet—prevents release of platelet granuoles that cause platelet aggregation. Mechanism is biphasic and dose-dependantHigh doses of aspirin can have negative effect on endothelial production of prostacyclin which prevents platelet accumulation on exposed collagen and dilates vessels.ASA PR qd x several weeks (often given at beginning of case)—5 grains (325 mg)No good studies to confirm benefit of useHematoma formation


Heparin

Naturally occuring glycosoaminoglycan which interrupts clotting cascade

Prevents transformation of prothrombin to thrombin, fibrinogen to fibrinDoes not lyse existing thrombi

Strongly adheres to endotheliumConcentration on endothelium 100x serum

½ life = 90 minutesGiven at time of first quarter of arterial anastomoses vs. at time of unclamping (bolus only vs. bolus with drip x 3 days)Literature unconvincing, although it may increase microvascular perfusion after ischemiaHematoma formationUsed as irrigation solutionLocal infusion may possibly be beneficial


Low molecular weight heparin

Appears to decrease vessel thrombosis in renal transplants (Broyer M, et al.,1991, Alkhunaizi AM, et al, 1998)


Flap monitoring

Clinical –”flap checks”Most commonly usedWarmthColorPin prickWound monitoring (hematoma, fistula)Frequency

MechanicalDoppler

Implanted vs. external vs. color flowOther


Clinical flap monitoring

Normal exam:Warm, good color, CRT 2-3 seconds, pinprick slightly delayed with bright red blood

Venous occlusion (delayed):Edema, mottled/purple/petechiae, tenseCRT decreasedPinprick – immediate dark blood, won’t stop

Arterial occlusion (usually <72hr):Prolonged CRT, temperature, turgorPalePinprick—little bleeding, very delayed


Mechanical flap monitoring

DopplerExternalImplanted

Buried flaps80-100% salvage (Disa J, et al 1999)

Color flow

Other


Antibiotics

8-20% of patients undergoing free tissue transfer will develop an infection despite intravenous antibiotic coverage.(Cloke DJ., et al, 2004)1 day vs. 5 day course of Clindamycin showed no significant difference in free flap survival (Carroll WR., et al., 2003)

Topical antibiotics in combination with intervenous antibiotics did not show a significant difference in post-operative complications after free tissue transfer (Simons JP, et al., 2001)


Free flap reconstruction—the costs

Longer ICU stay, more expensive, longer OR time (McCrory AL, et al., 2002)







SourcesBroyer M, Gagnadoux MF, Sierro A, Fischer AM, Niaudet P. Preventive treatment of vascular thrombosis after kidney transplantation in children with low molecular weight heparin. Transplant Proc 1991; 23: 1384. Alkhunaizi AM, Olyaei AJ, Barry JM, et al. Efficacy and safety of low molecular weight heparin in renal transplantation. Transplantation 1998; 66: 533. Nahabedian MY. Singh N. Deune EG. Silverman R. Tufaro AP. Recipient vessel analysis for microvascular reconstruction of the head and neck. [Journal Article] Annals of Plastic Surgery. 52(2):148-55; discussion 156-7, 2004 Feb. McCrory AL. Magnuson JS. Free tissue transfer versus pedicled flap in head and neck reconstruction. [Journal Article] Laryngoscope. 112(12):2161-5, 2002 Dec. Kroll SS. Robb GL. Reece GP. Miller MJ. Evans GR. Baldwin BJ. Wang B. Schusterman MA. Does prior irradiation increase the risk of total or partial free-flap loss?. [Journal Article] Journal of Reconstructive Microsurgery. 14(4):263-8, 1998 May. Jones NF. Johnson JT. Shestak KC. Myers EN. Swartz WM. Microsurgical reconstruction of the head and neck: interdisciplinary collaboration between head and neck surgeons and plastic surgeons in 305 cases. [Journal Article] Annals of Plastic Surgery. 36(1):37-43, 1996 Jan.Foote RL. Olsen KD. Meland NB. Schaid DJ. Kunselman SM. Tumor-ablative surgery, microvascular free tissue transfer reconstruction, and postoperative radiation therapy for advanced head and neck cancer. [Journal Article] Mayo Clinic Proceedings. 69(2):122-30, 1994 Feb. Cloke DJ. Green JE. Khan AL. Hodgkinson PD. McLean NR. Factors influencing the development of wound infection following free-flap reconstruction for intra-oral cancer. [Journal Article] British Journal of Plastic Surgery. 57(6):556-60, 2004 Sep.


SourcesBraun S. Mine R. Syed SA., et al. The optimal sequence of microvascular repair during prolonged clamping in free flap transfer. Plastic and Reconstructive Surgery 111(1):233-241, 2003Banic A. Krejci V. Erni D., et al. Effects of sodium nitroprusside and phenylephrine on blood flow in free musculocutaneous flaps during general anesthesia. Anesthesiology 90(1):147-155, 1999German G. Steinau HU. The clinical reliability of vein grafts in free flap transfer. Journal of Reconstructive Surgery 67:194-199, 1996Nahabedian MY. Bahram M. Manson PN. Factors associated with anastomotic failure after microvascular reconstruction of the breast. Plastic and Reconstructive Surgery 114(1):74-82, 2004Nahabedian M. Singh N. Deune EG. Recipient vessel analysis for microvascular reconstruction of the head and neck. Annals of Plastic Surgery 52(2):148-155, 2004Disa JJ. Polvora VP. Pusic AL Singh B. Cordeiro P. Dextran-related complications in head and neck microsurgery: Do the benefits outweigh the risks? A prospective randomized analysis. Head and Neck Microsurgery 112(6):1534-1539, 2001 Carroll WR. Rosenstiel D. Fix JR. de la Torre J. Solomon JS. Brodish B. Rosenthal EL. Heinz T. Niwas S. Peters GE. Three-dose vs extended-course clindamycin prophylaxis for free-flap reconstruction of the head and neck. [Clinical Trial. Journal Article. Randomized Controlled Trial] Archives of Otolaryngology -- Head & Neck Surgery. 129(7):771-4, 2003 Jul. Simons JP. Johnson JT. Yu VL. Vickers RM. Gooding WE. Myers EN. Pou AM. Wagner RL. Grandis JR. The role of topical antibiotic prophylaxis in patients undergoing contaminated head and neck surgery with flap reconstruction. [Clinical Trial. Journal Article. Randomized Controlled Trial] Laryngoscope. 111(2):329-35, 2001 Feb.


SourcesShindo M., Costantino P., Nalbone V., et al., Use of a mechanical microvascular anastomotic device in head and neck free tissue transfer. Archives of Otolaryngology—Head & Neck Surgery 122(5):529-532, 1996.De Lorenzi F., van der Hulst R., Boeckx W., et al., VCS auto suture stapled microvascular anastomoses in lower leg free flaps. Plastic and Reconstructive Surgery 109(6):2023-2030, 2002DeLacure M., Kuriakose M., Spies A., et al., Clinical experience in end-to-side venous anastomoses with a microvascular anastomotic coupling device in head and neck reconstruction. Archives of Otolaryngology—Head and Neck Surgery 125(8):869-872, 1999Ahn C., Shaw W., Berns S., et al., Clinical experience with the 3M microvascular coupling anastomotic device in 100 free-tissue transfers. Plastics and Reconstructive Surgery 93:1481-1484, 1994Berggren A., Ostrup L., Lidman D., et al., Mechanical anastomosis of small arteries and veins with the Unilink apparatus: a histologic and scanning electron microscopic study. Plastic and Reconstructive Surgery, 80:274-283, 1987Swartz W., Banis J., Head and Neck Microsurgery. Williams & Wilkins, Baltimore, MA, c.1992Baker S. Microsurgical Reconstruction of the Head and Neck. Churchill Livingstone, New York, NY, c.1989Panje W., Moran W. Free Flap Reconstruction of the Head and Neck. Thieme Medical Publishers, Inc., New York, NY c.1989Velanovich V. Smith DJ. Robson MC. Heggers JP. The effect of hemoglobin and hematocrit levels on free flap survival. American Surgeon 54(11):659-663, 1988Quinlan J. Anaesthesia for reconstructive free flap surgery. Anesthesia and Intensive Care Medicine The Medicine Publishing Company, Ltd., c.2003


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Microvascular Free Tissue Transfer / orthodontic courses by Indian dental academy

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